Introducing specificity and sensitivity in imaging mass spectrometry

在这项研究提案中，我们将利用我们在成像质谱学(IMS)方面的专业知识来解决生物成像领域尚未满足的重要需求。因此，这项建议将侧重于开发分析方法，以提高IMS分析几类临床相关内源性分子的特异性和敏感性。必须开发敏感和有针对性的方法，以便于确定可用于疾病诊断或预后或作为治疗反应指标的分子靶点。在法医学领域也可以开发这种有针对性的方法。将探索三个主要研究轴线：1)开发化学定制表面，以特别增强对薄组织切片中脂质和代谢物的检测，同时保持其空间完整性。随着纳米材料的快速发展，表面辅助激光二极管阵列IMS(Saldi IMS)的出现，为低分子化合物的成像开辟了新的前景。我们建议开发几种基于金和硅的Saldi表面，经过各种化学处理和精确织构，以增强解吸/电离和分析物特异性。此外，更好地控制表面疏水性将极大地减少分析物的离域。2)提出了解吸电喷雾电离(DESI)IMS分析组织切片中肽、脂类和代谢物的原位衍生化化学方法。多肽(和蛋白质)是利用DESI IMS从组织切片中分析更具挑战性的生物分子。肽N或C端衍生化使用含有固定电荷的亲水反应基团的新型化学方法增强了肽的溶解性，并消除了电喷雾电离离子抑制效应。这种反应性标签可以在IMS过程之前或期间(反应性DESI)贴在组织上。3)将开发创新的方法，专门探测和绘制潜在指纹中所含遗传物质的地图，目的是查明可疑性别。这方面是法医界最感兴趣的。为了针对特定性别的基因，将开发出通过光切割基团与带电报告离子偶联的互补DNA探针。在靶上喷射沉积和探针孵化后，LDI IMS可以精确地定位潜在指纹中可光解报告离子的位置。通过他的研究计划，在IMS方法开发方面的持续努力将使我们能够对法医和生物样本中的分子进行更深入和独特的分析，以补充我们实验室已经开发和可用的分子分析。总体而言，这些新方法将有助于广泛的生物应用，包括人类疾病和障碍，以及了解细胞、器官和整个生物体的正常发育和功能。

In this research proposal, we will leverage our expertise in Imaging Mass Spectrometry (IMS) to address important unmet needs in the field of biological imaging. Accordingly, this proposal will focus on the development of analytical methods to improve the specificity and sensitivity of IMS for the analysis of several classes of clinically relevant endogenous molecules. Sensitive and targeted methods must be developed to facilitate the identification of molecular targets that can be used in the diagnosis or prognosis of disease or as indicators of therapeutic response. Such targeted approaches can also be developed in the field of forensic science. Three main axes of research will be explored: 1) The development of chemically tailored surfaces to specifically enhance the detection of lipids and metabolites from thin tissue sections while maintaining their spatial integrity. The emergence of Surface-Assisted LDI IMS (SALDI IMS), fostered by the rapid development of nanomaterials, has created new prospects for the imaging of low molecular weight compounds. We propose to develop several gold and silicon-based SALDI surfaces precisely textured and treated with various chemistries to enhance desorption/ionization and analyte specificity. Further, a better control of surface hydrophobicity will greatly minimize analyte delocalization. 2) The development of in situ derivatization chemistries for the analysis of peptides, lipids and metabolites by desorption electrospray ionization (DESI) IMS from tissue sections is proposed. Peptides (and proteins) are more challenging biomolecules to analyze by DESI IMS from tissue sections. Peptide N or C-terminal derivatization novel chemistries using hydrophilic reactive groups containing a fix charge enhances peptide solubility and eliminates electrospray ionization ion suppression effects. Such reactive tags can be applied on tissue before or during (reactive DESI) the IMS process. 3) Innovative approaches will be developed to specifically detect and map genetic material contained within latent fingerprints with the goal of identifying the suspect gender. This aspect is of prime interest to the forensic community. To target gender specific genes, complementary DNA probes coupled to a charged reporter ion via a photocleavable group will be developed. After on-target spray deposition and probe incubation, the precise location of the photocleavable reporter ion within the latent fingerprint can then be mapped by LDI IMS. Through his research program, continued efforts in IMS method development will allow a deeper and unique analysis of molecules from forensic and biological samples complementary to those already developed and available in our laboratory. Overall, these new methods will be useful for a wide range and biological applications including human diseases and disorders as well as understanding normal development and functioning of cells, organs and whole organisms.